1. Field of the invention
This invention relates to a polycrystal diamond fluted tool and a process for the production of the same. The polycrystal diamond tool of the present invention provides a largely improved rotary tool having superior performance as compared to the sintered diamond tool of the prior art.
2. Description of the Prior Art
A diamond compact obtained by sintering diamond powder with a binder metal at an ultra-high pressure and a high temperature at which diamond is stable has the features of diamond with the highest hardness of all tool materials and does not tend to break by cleavage at a low stress as in the case of single crystal diamond. Thus, this diamond compact has been used as a cutting tool, wire drawing die, dresser, rock excavator or the like.
On the other hand, end mills, drills and reamers have been developed using sintered dies as tool materials. However, it is very difficult technically to produce a flute-shaped material by sintering at an ultra-high pressure and it is expensive to form a flute by after-working, so at the present time, such tools have been limited to straight fluted base metals or tool base metals subjected to helical grinding, which are brazed with plate-shaped tool materials.
These tools have disadvantages that the cutting edge strikes on a workpiece at a stroke, so that the cutting resistance is rapidly changed and the dimensional accuracy is lowered. Furthermore, a problem arises in that chips are not discharged well and the surface roughness of a workpiece is not good, because of not being fluted.
In order to solve these problems, there has been developed a fluted rotary tool of cemented carbide, whose cutting part is coated with a thin layer of polycrystal diamond by a vapor phase synthetic method. However, this tool has not been put to practical use yet because of the problem that the adhesiveness between a cemented carbide substrate and coating film is not sufficient and consequently, the coating film tends to be stripped during use.